Leftover World War II ammunition buried in a forest outside Berlin is complicating efforts to contain wildfires raging through Germany and the rest of Europe.

In the Treuenbrietzen region, just 30 miles outside of the country’s capital, firefighters are attempting to contain wildfires scorching an area larger than 500 football fields, but are having trouble getting close.

Because of battles raged in the areas around Berlin during WWII, as the Allies closed in on the Nazis, forgotten ammunition left behind at these sites pose a threat to first responders.

“The ammunition is very dangerous because one cannot step on the ground and therefore one cannot get close to the fire,” Dietmar Woidke, minister-president of nearby Brandenburg, told reporters.

Instead, firefighters are attempting to contain the wildfires remotely, using helicopters to collect water from rivers then dumping them into the fires.

In other instances, water cannons are being used to extinguish the flames.

Three villages in the path of the fires were evacuated, and some Berlin residents were warned to stay indoors and keep their windows closed as smoke blew into the city.

Germany has had almost no rain this summer, and hundreds of firefighters and soldiers have been sent to all parts of the country to tackle wildfires.